Add behavioral test checking if GIL is disabled

Author: zanieb

src/validation.rs

@@ -2087,6 +2087,7 @@ fn verify_distribution_behavior(dist_path: &Path) -> Result<Vec<String>> {
         .stdout_to_stderr()
         .unchecked()
         .env("TARGET_TRIPLE", &python_json.target_triple)
+        .env("BUILD_OPTIONS", &python_json.build_options)
         .run()?;
 
     if !output.status.success() {

src/verify_distribution.py

@@ -141,6 +141,20 @@ def test_ssl(self):
 
         ssl.create_default_context()
 
+    @unittest.skipIf(
+        sys.version_info[:2] < (3, 13),
+        "Free-threaded builds are only available in 3.13+",
+    )
+    def test_gil_disabled(self):
+        import sysconfig
+
+        if "freethreaded" in os.environ.get("BUILD_OPTIONS", "").split("+"):
+            wanted = 1
+        else:
+            wanted = 0
+
+        self.assertEqual(sysconfig.get_config_var("Py_GIL_DISABLED"), wanted)
+
     @unittest.skipIf("TCL_LIBRARY" not in os.environ, "TCL_LIBRARY not set")
     @unittest.skipIf("DISPLAY" not in os.environ, "DISPLAY not set")
     def test_tkinter(self):